Prof D Chandrasekharam

These three are intimately related! One causes global warming while the other  controls global warming!!

 Over centuries, civilizations used firewood, biomass and dung cake to sustain its lives. For both cooking and heating purposes this was and is the cheap and easily available stock to humans. Excess use of any such energy sources is harmful and the consequences are being felt by the current generation. In the current industrial era, besides the above fuels, fossil fuels like coal, diesel and kerosene enhanced the BC content in the atmosphere further to our misery!!  Changing weather pattern, unusual melting of glaciers, droughts, flood are the consequences of such uncontrolled black carbon emissions. Carbon dioxide also plays a major role but CO₂ has a long term effect while BC has a short term effect. 

Coal, fuel wood, dung cake and agricultural waste are consumed maxium in that order in India. According to 1996-2001 data, 286 Mt of coal, 302 Mt of fuel wood, 121 Mt of dung cake and 116 Mt of agricultural waste is consumed in India.  BC emission factor of these fuels in that order is 0.8, 1.1, 4.4 and 1.3 g/kg. 

BC  absorbs sunlight turning it into heat. Thus a layer of BC in the atmosphere, while emitting a third of this absorbed heat back in to space, keeps the earth’s surface warm. More BC in the atmosphere means more heat over the surface. As the BC increases the earth’s surface gets hotter and hotter!! Simple logic.  Thus BC causes change in the heat input at the top of the atmosphere. This is known as “forcing”.  According to the Intergovernmental Panel on Climate Change (IPCC) 2007 report,  forcing of BC is of the order of + 0.34 W/m² while forcing of CO₂ is of the order of + 1.66 W/m². 

 The residence time of BC in the atmosphere is about a week while CO₂’s is several decades. So BC does not accumulate while CO₂ accumulates in the atmosphere. What it means is that through controlling BC emissions, global warming can be controlled within in a short period of time.  It is very easy to control BC emissions without compromising life comforts!! 

More about BC soon..